This invention relates to Si bearing, corrosion resistant Cu—Ni alloys that are especially suited for use in food processing equipment. The alloys can also be used in other sliding metal applications in the form of bearings, bushings, blades, gears, guides, slides, vanes, impellers and other components. This highly wear resistant alloy may be continuously or statically cast, and it may be mechanically treated into different shapes. The alloy may be described as a silicized dairy metal.
Prior to 1990, lead containing Cu—Ni—Sn—Zn alloys popularly known as “Dairy Metals” were used in food processing machines. Other names for these metals are “Dairy Bronze”, “German Silver” and “Nickel Silver.” Health concerns regarding Pb led to its replacement by Bi and/or Se. Many Cu-base alloys (See, for example, Rushton, U.S. Pat. No. 4,879,094; Lolocano et. al., U.S. Pat. No. 5,167,726; Sahu, U.S. Pat. No. 5,242,657; Singh, U.S. Pat. No. 5,330,712; Sahu, U.S. Pat. No. 5,413,756; Singh, U.S. Pat. No. 5,487,867; King et. al., U.S. Pat. No. 5,614,038; Sahu, U.S. Pat. No. 5,846,483; Sahu, U.S. Pat. No. 6,059,901; and Smith, U.S. Pat. No. 6,149,739).
Some of these alloys (such as, for example, Sahu, U.S. Pat. Nos. 5,242,657; Sahu U.S. Pat. No. 5,846,483; Sahu, U.S. Pat. No. 6,059,901; and Smith, U.S. Pat. No. 6,149,379) are used in contact with comestibles in food forming equipment. Sometimes aluminum bronzes like C954 are also used. However, these alloys are relatively soft and wear out quickly. Aluminum bronzes have poor corrosion resistance and turn green during use, so they should not be used in contact with food. The following Table 1 lists properties of alloys disclosed in the aforementioned patents as well as bronze C954. Properties disclosed are well known in the art and include tensile strength measured in KSI, yield strength measured in KSI, percent elongation, and hardness measured in BHN (Brinnel hardness number).
TABLE 1Hardness and Mechanical Properties ofCertain Dairy Metals and Al Bronze (C954)Dairy Metals Covered byAlDifferent U.S. PatentsBronzeU.S. U.S.U.S.U.S.C954Pat. No.Pat. No.Pat. No.Pat. No.(CDA5,242,6575,846,4836,059,9016,149,379Data)Tensile20-3040-5542-585575Strength (KSI)Yield Strength18-2828-3534-453030(KSI)% Elongation0.5-3.0 5-103-81312(in 2 inches)Hardness110-140110-155110-140130170(BHN)
Therefore, a goal of certain preferred embodiments of this invention is to provide a moderate cost alloy with higher hardness and wear resistance that maintains good corrosion and anti-galling characteristics coupled with high strength and good ductility.